This invention relates generally to a battery separator and, more particularly, to an apparatus for fabricating a battery separator from two sheets of microporous plastic material adhered together by two strips of polyvinyl chloride material to form a sleeve.
It is known that wet cell-type batteries employ at least one pair of opposite-polarity, planar electrodes, commonly called plates, which are closely spaced in a parallel relationship and immersed in a liquid electrolyte to form an electrochemical couple. Many wet cell-type batteries employ a plurality of pairs of the opposite-polarity plates, with the plates being normally arranged in an upstanding, face-to-face configuration. The exact number of pairs of plates in a particular battery depend upon the capacity and/or voltage desired.
In order to prevent adjacent, opposite-polarity plates from coming into direct physical contact, and thereby causing arcing and/or short circuiting, it is necessary to electrically insulate the adjacent plates from each other. Electrically insulative material, usually in sheet form and similar in size to the plates, and commonly referred to as separators, have been positioned between the opposite-polarity plates, with the insulative material being permeable or semi-permeable to the liquid electrolyte to maintain the ionic conduction required for the battery action.
In the prior art, separators have been fabricated of rubber, wood and glass. More recent designs have used microporous material, including polyethylene, vinyl resin, and the like, which have excellent insulating capabilities, yet are relatively low in weight and cost. An example of such a plastic separator is disclosed in U.S. Pat. No. 3,696,061, issued Oct. 3, 1972, in the name of Selsor et al, and assigned to the same assignee as the present application.
In applications where heavy-duty use and requirements are such that maximum insulation between the positive and negative plates must be provided, such as in the case of industrial batteries, it has been found advantageous to place a sleeve of insulating material upon either the positive or the negative plates, with the sleeve being formed and folded to the dimensions of the plate. In a typical insulating-sleeve configuration, one side is formed by the end portions of the sleeve which are overlapped and sealed, so that the sleeve has completely insulating sides to prevent the formation of lead dendrites from the negative to the positive plates when the battery is charging and discharging in service.
Although battery separators of a plastic material of the general type disclosed above, and as specifically disclosed in the aforementioned Selsor et al patent, have enjoyed widespread commercial success, especially for use in industrial type batteries, such separators are relatively brittle and therefore special means are required to fold the material into the desired sleeve configuration without fracturing or breaking the material. For example, in the commonly-assigned U.S. Pat. No. 4,002,417, issued Jan. 11, 1977, there is disclosed a relatively complex and relatively expensive apparatus for folding such separator material to form sleeves or envelopes without causing fracture or breakage of the material.
In U.S. patent application Ser. No. 726,264, filed Sept. 24, 1976, now U.S. Pat. No. 4,086,119 and assigned to the same assignee as the present application, a method is disclosed for forming a sleeve-type battery separator without the need for folding the separator material. This method has proven to be relatively successful, and underscores the need for a simple machine for fabricating a battery separator of this type without folding of the separator material.